Commitments and Contingencies - Future Minimum Rental Payments (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
2018 (remaining)	$ 914,000		$ 914,000
2019	1,968,000		1,968,000
2020	1,963,000		1,963,000
2021	1,963,000		1,963,000
2022	1,917,000		1,917,000
2023 and thereafter	33,775,000		33,775,000
Total	42,500,000		42,500,000
Other Expenses [Abstract]
Operating ground lease expense	$ 543,000	$ 311,000	$ 952,000	$ 623,000